I'll look back thru a pile of my stuff, I doubt the 39-2 (or many) boats have coring below the waterline. (now watch, 50 people will say "MINE IS")
I've had to recore parts of the deck, but the hull is sound. The boat was built in 1981. I agree with what Paul says about coring. By the way, the J30 was built by Pearson (JBoats designs boats and outsources the builds).